The removal of the delay is in preparation of moving the program to a
Systemd service -- instead of a '@reboot' cronjob. By doing that, the need
to wait for the network stack on the Raspberry Pi to start is a built-in
feature.
The change to Systemd is becuase the program would terminate when it hits
the 'max. requests exceeded' exception in the 'requests' module (Python).
Having spoke to Nic (lead artist), she has stated she has a preference for
the program to be requesting the latest light readings or nothing at all.
The 'backoff' features which come with the 'requests' module will stop the
program from crashing but at the possibility of the having the Relays be
out-of-sync -- whilst still looking like it's working -- with the latest
light readings produced by the Light Meters in the factory and what's been
delivered to the server (Midpoint).
To be fair, this problem only arose when I ran the two gallery Relays, one
Light Meter and one instance of Eyes and Ears from the same location (my
flat). This wouldn't be the case in the when the exhibiton is live. Either
way, Systemd it is.
The natural process of waiting for the program to restart (with added delay
in Systemd service file if wanted) naturally allows the system to 'backoff'
but it keeps the all-or-nothing aspect Nic prefers.
The exception message is a minor change. It's there just to make it easier
to determine if the program is terminating because of the 'max. requests
exceeded' exception. I added it to the generic exception for ease more than
anything else. I can catch other exceptions whilst expecting the 'max.
requests' one. This is not the best approach to programming but the
trade-off between project goals and budget make me think this is ok (for
now). It is what it is.
The light meter readings changed when new a Light Meter (factory2) was installed (new components). The change produces different light levels (don't know why but probably different components). This change accounts for the new levels and the light which is controlled by this code now turns on when it receives a reading greater than 48. This seems to be the baseline light level in the welding booth (in Ritherdon, the factory) -- after monitoring the readings for a period of time.
The URL before was for adding a light reading -- not getting a reading. This URL change fixes that. This is what happens when you copy-and-paste code from the Light Meter project into this one.
The module is used to help determine which device is running the program. The device name allows the rest of the system to know what this device needs when I makes it RESTAPI calls.
The device/host names for the devices running this program should be using 'galleryX' ('X' denotes the device number). I put 'factory' instead of gallery because I'm an idiot. 'factory' are the device names for the Light Meter project.
This adds a check to determine which relay the system is (hostname/device name). When name is determined,the URL the program will use for the RESTAPI call is then set. At the time of writing, the system is expecting two relays. Hence the if-else statement. If more devices are to be added, this approach will need to be reconsidered.
The API calls now go to rither.abbether.net instead of the designated IP
address assigned the server (AWS). This change makes it easier to access the
RestAPI (see midpoint repo.) server. The URL will remain constant and if the
server needs to be powered-down/restarted for anything, the new IP address
Amazon (web services) assigns to it will no longer matter. And, the code used
to make the RestAPI call will no longer need changing manually.
gallery2
Craig Oates
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